In most conventional computer keyboards, a foam sensor is inserted into a slot of a cylindrical shaped seat. This seat passes through the seat of a carter base. A plurality of holes are formed in the base. In each hole, a seat and a push button, mounted with a spring, are inserted. A plate for the button is also associated with each cylindrical seat. Finally, a housing is provided. These prior art structures are complicated, they involve a large number of components, and thus they are costly to manufacture.
Further, the method of mounting the button and the cylinderical seat employed a clip plate to clip the button to the seat. This mounting method is unsatisfactory because if the mounting or clipping force was insufficient, it was possible for the button to drop off during transportation. Also, if the mounting force was overly aggressive, again it was possible for the button to drop off.
Yet another disadvantage is that, due to the spring bearing on the button, the user could be fooled into thinking the operation was complete when in fact there was no operation of the foam sensor or mechanical switch. Thus, the operator had to watch the monitor to know whether or not operation of the button has achieved an input operation or not.
For conventional buttons, mechanical switches or conductive rubber capacitor types of switches are used to produce the output signals. Mechanical switches are reliable and their contacts are not effected by the weather, but their cost of installation is prohibitively high. The capacitor types, which use a metallic foil at the bottom of a foam sensor to produce a signal from the circuit board, possess the benefits of low cost and low cost of installation; however, they are effected by the weather. Oxidation of metal increases electrical resistance, which causes a poor magnetic field, which has an adverse effect on the output signal.